JP7600371B2 - Piezoelectric elements and piezoelectric sensors - Google Patents

Description

Disclosed embodiments relate to piezoelectric elements and piezoelectric sensors.

Conventionally, a piezoelectric element has been known that has a laminate in which a piezoelectric body and an internal electrode are stacked, and an external electrode connected to the internal electrode.

JP 2020-167225 A

The piezoelectric element according to one aspect of the embodiment includes a laminate and an external electrode. The laminate is formed by stacking a plurality of piezoelectric bodies and internal electrodes. The external electrode is located on a side of the laminate and is connected to the internal electrode. The laminate has an active region sandwiched between the internal electrodes having different polarities and an inactive region sandwiched between the internal electrodes having the same polarity. The internal electrode contains Ag and Pd as main components. The active portion of the internal electrode located in the active region is a first portion. The inactive portion of the internal electrode located in the inactive region has a second portion having a higher Pd content than the first portion. The first portion has a higher Ag content than the second portion.

FIG. 1 is a cross-sectional view illustrating an example of a piezoelectric element according to an embodiment. 2 is a cross-sectional view of the piezoelectric element shown in FIG. 1 taken along line AA. 3 is a cross-sectional view of the piezoelectric element shown in FIG. 1 taken along the line BB. FIG. 4 is a cross-sectional view (part 1) showing an example of a piezoelectric element according to a modified example of the embodiment. FIG. 5 is a cross-sectional view (part 2) showing an example of a piezoelectric element according to a modified example of the embodiment. FIG. 6 is a plan view illustrating an example of a piezoelectric element according to a modified example of the embodiment. FIG. 7 is a cross-sectional view (part 3) showing an example of a piezoelectric element according to a modified example of the embodiment. FIG. 8 is a cross-sectional view (part 4) showing an example of a piezoelectric element according to a modified example of the embodiment. FIG. 9 is a perspective view illustrating an example of a piezoelectric sensor according to the embodiment. 10 is a cross-sectional view of the piezoelectric sensor shown in FIG. 9 taken along the line CC.

Below, embodiments of the piezoelectric element and piezoelectric sensor disclosed in the present application will be described with reference to the attached drawings. Note that the present disclosure is not limited to the embodiments shown below. It should be noted that the drawings are schematic, and the dimensional relationships between the elements, the ratios between the elements, etc. may differ from reality.

<Piezoelectric element>
Fig. 1 is a perspective view showing an example of a piezoelectric element according to an embodiment. Fig. 2 is a cross-sectional view taken along the line A-A of the piezoelectric element shown in Fig. 1. Fig. 3 is a cross-sectional view taken along the line B-B of the piezoelectric element shown in Fig. 1. Fig. 2 corresponds to a cross-sectional view of the piezoelectric element 1 shown in Fig. 1 taken along the ZX plane. Fig. 3 corresponds to a cross-sectional view of the piezoelectric element 1 shown in Fig. 1 taken along the XY plane so as to include the internal electrode 30.

The piezoelectric element 1 according to the embodiment includes a laminate 10 and an external electrode 40. The piezoelectric element 1 is, for example, a piezoelectric sensor that detects an external force applied to the laminate 10 and converts it into a voltage.

The laminate 10 is made up of multiple layers of piezoelectric bodies 20 and internal electrodes 30. The piezoelectric bodies 20 are made of, for example, a ceramic material having ferroelectric properties.

The internal electrode 30 contains Ag and Pd as the main components. Here, "main components" refers to the fact that, among the various components constituting the internal electrode 30, Ag and Pd are contained in greater amounts than the other components. Of the total components constituting the internal electrode 30 (100% by mass), Ag is 0.5 to 99.5% by mass, Pd is 0.5 to 99.5% by mass, and the total of Ag and Pd is 70% by mass or more. In addition, the "other components" referred to here are, for example, glass. For example, when the total of Ag and Pd is 70% by mass, the remaining 30% by mass is glass. On the other hand, there may be almost no glass, Ag is 99.5% by mass, Pd is 0.5% by mass, or Ag is 0.5% by mass and Pd is 99.5% by mass.

The internal electrode 30 includes electrodes 31 to 34. Electrodes 31 to 34 are stacked in order with the piezoelectric body 20 in between. One end of electrodes 31 and 33 is electrically connected to electrode 41, which is the external electrode 40, and extends along the XY plane in the positive direction of the X-axis. One end of electrodes 32 and 34 is electrically connected to electrode 42, which is the external electrode 40, and extends along the XY plane in the negative direction of the X-axis.

The external electrode 40 contains Au as a main component. The external electrode 40 may be a so-called gold electrode containing, for example, more than 50 mass%, particularly 90 mass% or more of Au or Au alloy. The external electrode 40 may also contain Pb (lead). For example, when the external electrode 40 located at the interface with the piezoelectric body 20 contains Pb, the external electrode 40 has high adhesion. When the piezoelectric body 20 contains Pb, the external electrode 40 has even better adhesion. The external electrode 40 is located on the side of the laminate 10 and is connected to the internal electrode 30. The external electrode 40 has electrodes 41 and 42 facing each other across the laminate 10. The electrode 41 is located on the side of the laminate 10 on the negative X-axis direction side. The electrode 42 is located on the side of the laminate 10 on the positive X-axis direction side. The external electrode 40 has a roughly rectangular shape that is longer in the Y-axis direction, in which the internal electrode 30 extends exposed outside the laminate 10, than in the Z-axis direction, which is the stacking direction of the internal electrode 30, along the side of the laminate 10.

The laminate 10 has an active region 11 and an inactive region 12. The active region 11 is a region sandwiched between internal electrodes 30 of different polarities. Specifically, the active region 11 is a region where adjacent internal electrodes 30 face each other.

The inactive region 12 is a region sandwiched between internal electrodes 30 of the same polarity. Specifically, the inactive region 12 is a region between electrodes 31 and 33 connected to the same external electrode 40 (41) where electrode 32 is not located, and a region between electrodes 32 and 34 connected to the same external electrode 40 (42) where electrode 33 is not located.

The active portion of the internal electrode 30 located in the active region 11 is the first portion 36. The inactive portion of the internal electrode 30 located in the inactive region 12 has a second portion 37 having a higher Pd content than the first portion 36. The first portion 36 has a higher Ag content than the second portion 37. The Ag and Pd contents are measured by EPMA (electron probe microanalyzer) after confirming the measurement point by observation with a SEM (scanning electron microscope). The contents of the first portion 36 are, for example, 70 to 95 mass% Ag and 5 to 30 mass% Pd, and the contents of the second portion are, for example, 0.5 to 15 mass% Ag and 85 to 99.5 mass% Pd.

Ag is more easily deformed than, for example, Pd, which constitutes the internal electrode 30. The first portion 36 has a higher Ag content than the second portion 37, which reduces the stress that occurs when the active region 11 deforms. This makes the piezoelectric element 1 highly durable.

Pd is less likely to deform than, for example, Ag that constitutes the internal electrode 30. Since the second portion 37 has a higher Pd content than the first portion 36, the inactive region 12 is less likely to deform. This makes the piezoelectric element 1 more durable.

Furthermore, the second portion 37, which has a high Pd content, may be a three-dimensional mesh structure, so that the internal electrode 30 itself has a stress relaxation function, or the space in the three-dimensional mesh may contain a glass layer or the like that has a strong bond with the piezoelectric body 20. This reduces the occurrence of microcracks between the second portion 37 and the piezoelectric body 20 even after long-term use, making the piezoelectric element 1 even more durable. The second portion 37 does not have to be located in the entire inactive region 12. In addition, when the piezoelectric element 1 is used as a piezoelectric sensor, the piezoelectric body 20 is also deformed in the portion of the inactive region 12 that contacts the active region 11 due to the stress applied to the piezoelectric element 1. At this time, since the first portion 36 contains a large amount of Ag, which is more easily deformed than Pd, etc., it can follow the deformation, and the piezoelectric element 1 has high durability.

To achieve the structure shown in Figure 2, for example, the following methods can be used.

The piezoelectric element 1 comprises a laminate 10 in which piezoelectric bodies 20 and internal electrodes 30 are alternately stacked. When the laminate 10 has a rectangular prism shape, for example, it has a length of 2 mm to 10 mm, a width of 2 mm to 10 mm, and a height in the stacking direction of about 1 mm to 20 mm. Note that the laminate 10 may have a shape other than a rectangular prism shape, such as a hexagonal prism shape, an octagonal prism shape, or a cylindrical shape.

The piezoelectric bodies 20 constituting the laminate 10 are made of piezoelectric ceramics. The average grain size of the piezoelectric ceramics is, for example, about 1.6 to 2.8 μm. Examples of piezoelectric ceramic materials include perovskite oxides such as lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), lithium niobate (LiNbO ₃ ), and lithium tantalate (LiTaO ₃ ).

The internal electrodes 30 are mainly composed of a metal such as Ag, Ag-Pd, Ag-Pt, or Cu, and are arranged alternately in the stacking direction. A first electrode is led out to one side of the laminate 10, and a second electrode is led out to the other side.

To form the internal electrode 30, pastes with different Ag and Pd ratios are printed on the piezoelectric body for the first portion 36 and the second portion 37 to form a laminate, which is then fired. The boundary between the first portion 36 and the second portion 37 can be controlled by the printing pattern. Also, a paste containing a large amount of Ag is printed at the position of the internal electrode 30 including the first portion 36 and the second portion 37 to form a laminate, which is then fired once. Next, a Pd paste may be printed at the position of the external electrode 40 and fired to form the second portion 37 containing a large amount of Pd at the end of the internal electrode 30 by utilizing the diffusion phenomenon. In this method, since the external electrode is made of Pd, it may be scraped off to form an external electrode 40 mainly composed of Au, for example.

There are various methods other than those mentioned above, and any of them may be used.

2 and 3, the first portion 36 may be located at the boundary between the active portion and the inactive portion. With this configuration, the Ag content is high at the boundary between the active portion and the inactive portion, so that the stress experienced by the boundary between the active region 11 and the inactive region 12 in particular can be reduced. This provides the piezoelectric element 1 with excellent durability.

The external electrode 40 may also be located within the second portion 37 in a side view. Figures 3 and 6 show this example. According to this configuration, the external electrode 40 does not have an interface with the first portion 36. Therefore, a triple interface is not generated between the external electrode 40, the first portion 36, and the second portion 37. For example, if the external electrode 40 has a high Au content, the first portion 36 has a high Ag content, and the second portion 37 has a high Pd content, stress may be applied to these triple interfaces due to differences in the contained components and amounts. However, according to the above configuration, a triple interface is not generated and the applied stress is small, so that the piezoelectric element 1 has excellent durability.

Figures 4 and 5 are cross-sectional views showing an example of a piezoelectric element relating to a modified embodiment. Figure 4 is a cross-sectional view taken along the line A-A of the piezoelectric element 1 shown in Figure 1. Figure 5 is a cross-sectional view taken along the line B-B of the piezoelectric element 1 shown in Figure 1.

The piezoelectric element 1 according to the modified example has a connection portion 35 located between the second portion 37 and the external electrode 40. The connection portion 35 has thermal conductivity intermediate between that of the second portion 37 and the external electrode 40. For example, when the second portion 37 contains Ag and Pd and has a higher Pd content than the first portion 36 and the main component of the external electrode 40 is Au, the connection portion 35 contains an alloy of Au and Pd. By having such a connection portion 35, heat is easily transferred from the second portion 37 to the connection portion 35 and from the connection portion 35 to the external electrode 40, so that the heat generated in the piezoelectric element 1 is easily released to the outside.

The connection portion 35 may also be an alloy of Au, Pd and Ag. The content of Au, Pd and Ag may be measured by EPMA after checking the measurement point by SEM observation. For example, Au is 30-70 mass %, Pd is 0.5-20 mass %, and Ag is 29.5-69.5 mass %. By constructing the connection portion 35 from a material with high strength and excellent thermal conductivity, it is possible to obtain a piezoelectric element 1 with excellent durability, which can be made smaller.

The connection part 35 may have a lower content of Ag and Pd than the active part. The Ag and Pd contents may be measured by EPMA after confirming the measurement points by SEM observation. For example, when the active part has 70-95% Ag by mass and 5-30% Pd by mass, the connection part 35 may have a lower content than these. In other words, the connection part 35 may contain metal components other than Ag and Pd.

For example, components such as Au contained in the external electrode 40 may be diffused into the connection portion 35. Furthermore, the components contained in the external electrode 40 that have diffused into the connection portion 35 may be an alloy of Ag and Pd. This makes it difficult for the external electrode 40 to peel off from the internal electrode 30.

The connection portion 35 may also contain Ag. This configuration can improve heat dissipation.

The external electrode 40 may contain Au and Ag as main components. In a specific example, the Au content is 70 to 95.5% by mass, and the Ag content is 4.5 to 30% by mass. The external electrode 40 may have a first region in contact with the piezoelectric body and a second region exposed to the outside. In this case, the first region may have a higher Ag content than the second region, and the second region may have a higher Au content than the first region. Ag is a component contained in the internal electrode 30 and has excellent thermal conductivity, so that heat generated by long-term element operation can be transferred to the external electrode 40 and dissipated. In addition, the second region exposed to the outside has a higher Au content than the first region, resulting in excellent corrosion resistance.

Figure 6 is a plan view showing an example of a piezoelectric element relating to a modified embodiment. Figure 6 is a plan view of the piezoelectric element 1 as seen from the external electrode 40 side. In comparison with Figure 1, it is a side view.

As shown in FIG. 6, the external electrode 40 may have a third portion 43 containing Ag. The third portion 43 may be located wider in the thickness direction (Z-axis direction) of the internal electrode 30 on the outer edge side than in the central portion along the width direction (Y-axis direction) of the internal electrode 30. Being located wider here means that it has a longer length in the Z-axis direction. In this way, when the external electrode 40 has the third portion 43, the external electrode 40 has high heat dissipation properties on the outer edge side and excellent electrical conductivity in the central portion.

Figures 7 and 8 are cross-sectional views showing an example of a piezoelectric element according to a modified embodiment. Both Figures 7 and 8 are other examples of the cross section of the piezoelectric element 1 shown in Figure 1 taken along the line A-A.

As shown in FIG. 7, the external electrode 40 has a layer 50 (first layer) and a layer 60 (second layer). The layer 50 contains Ag as a main component and is a layer that is in contact with the piezoelectric body 20. The layer 60 contains Au as a main component and is a layer that is exposed to the outside. The "main component" here refers to a component that exceeds 50% of the total components that make up the layers 50 and 60, respectively.

The external electrode 40 in the piezoelectric element 1 shown in Figure 8 has a layer 50 and a layer 60. Layer 50 is in contact with the piezoelectric body 20 and is located on the inner surface side of the external electrode 40. Layer 50 has, for example, an Au content of 10 to 40 mass % and an Ag content of 60 to 90 mass %.

Layer 60 is located away from piezoelectric body 20 and on the outer surface side of external electrode 40. Layer 60 has a higher Au content than layer 50. Specifically, the Au content of layer 60 is 70 to 95.5 mass %, and the Ag content is 4.5 to 30 mass %.

Since the external electrode 40 has layers 50 and 60 of the above configuration, the external electrode 40 and the piezoelectric body 20 have excellent adhesion. In addition, the piezoelectric element 1 can be used stably for a long period of time even if the atmosphere outside the piezoelectric element 1 is a hot and humid environment. Furthermore, the piezoelectric element 1 can be made into a general-purpose element that allows wire bonding and various other connections to be made in order to establish electrical continuity between the piezoelectric element 1 and an external circuit.

Furthermore, in the piezoelectric element 1 shown in Figure 8, when layer 60 covers and surrounds layer 50 in contact with piezoelectric body 20, it can be used stably for a long period of time even in harsh environments.

7 and 8, the external electrode 40 may be formed by, for example, printing and firing a layer containing mainly Ag on the surface of the laminate 10 as the first layer of the external electrode 40, positioning layer 50, and then printing and firing a layer containing mainly Au on the surface of layer 50 to position layer 60. In the piezoelectric element 1 thus fabricated, the second portion 27 of the internal electrode 30 located in the inactive region 12 can be selectively positioned at the boundary with the external electrode 40.

Note that, although Figures 7 and 8 illustrate an example in which the external electrode 40 has layers 50 and 60, one or more layers different from layers 50 and 60 may be provided between layers 50 and 60.

<Piezoelectric sensor>
Fig. 9 is a perspective view showing an example of a piezoelectric sensor according to an embodiment, and Fig. 10 is a cross-sectional view taken along the line CC of the piezoelectric sensor shown in Fig. 9.

9 and 10, the piezoelectric sensor 100 according to the embodiment includes a piezoelectric element 1 and a case 3 surrounding the piezoelectric element 1. The case 3 includes a convex portion 3A that protrudes inward from the inner surface 4b of the case body. The end face 3a of the convex portion 3A abuts against the end face 1a of the piezoelectric element 1 and is located inside the outer periphery of the end face 1a of the piezoelectric element 1.

When pressure is applied to the piezoelectric sensor 100 as shown by the white arrows in Figures 9 and 10, the pressure is applied to the piezoelectric element 1 through the case 3. The piezoelectric sensor 100 outputs to the outside a voltage generated by the pressure being applied to the piezoelectric element 1. The magnitude of the pressure is calculated from the magnitude of this voltage.

In the piezoelectric sensor 100 of this embodiment, the piezoelectric element 1 is stored in the internal space of the cylindrical case 3. In order to transmit the pressure applied to the outer surface 4a of the case 3 to the piezoelectric element 1, the piezoelectric element 1 is sandwiched between the upper and lower walls of the case 3 and stored. The outer surface 4a located on the upper side of the case 3 is the surface to which external force is applied, and the end surface 3a of the convex portion 3A provided on the inner surface 4b (top surface of the internal space) of the case 3 facing it abuts against the upper end surface (end surface 1a) of the piezoelectric element 1. The end surface 3a of the convex portion 3A is the surface that transmits the external force to the piezoelectric element 1. The end surface 3a of the convex portion 3A abuts against one end surface 1a (upper end surface) in the stacking direction of the piezoelectric element 1, and the other end surface 1b (lower end surface) abuts against the inner surface 5b (bottom surface of the internal space) facing the outer surface 5a located on the lower side of the case 3.

The piezoelectric sensor 100 of this embodiment has a lead terminal 7 extending from the internal space of the case 3 to the outside. The lead terminal 7 is electrically connected to the piezoelectric element 1. The voltage generated in the piezoelectric element 1 is output to the outside via the lead terminal 7.

The piezoelectric sensor 100 of this embodiment uses a highly durable piezoelectric element 1, making the piezoelectric sensor 100 highly durable.

Figure 9 is a perspective view showing an example of a piezoelectric sensor 100 equipped with a piezoelectric element 1, and Figure 10 is a cross-sectional view taken along the line C-C. The case 3 is made of a metal material such as stainless steel (e.g., SUS304 or SUS316L according to the JIS standard). The case 3 is a container having a space inside for storing the piezoelectric element 1. In the example shown in Figure 9, the case 3 has a cylindrical or disc-shaped appearance, but is not limited to this. In the case of a cylinder, the upper wall (top plate 4) to which an external force is applied is circular, so that it deforms uniformly when an external force is applied. Therefore, it is preferable that the end face 3a of the convex portion 3A on the inside of the upper wall abuts against the end face 1a of the piezoelectric element 1 without tilting.

The shape of the protrusion 3A may be a flat end surface 3a that abuts against the end surface 1a of the laminate 10 of the piezoelectric element 1 in the stacking direction. The shape of the protrusion 3A may be, for example, a rectangular column, a hexagonal column, an octagonal column, or a truncated pyramid shape in which the case body side is larger than the end surface 3a, or a cylindrical or truncated cone shape as shown in Figures 9 and 10. The case 3 has, for example, an outer dimension of 4 mm to 20 mm in diameter and 2.5 mm to 25 mm in height, and an internal space of 3.4 mm to 19.8 mm in diameter and 1.3 mm to 24.8 mm in height. The thickness of the case 3 excluding the protrusion 3A is, for example, set to 0.1 mm to 1 mm. The protrusion 3A has, for example, an end surface 3a with a diameter of 1.2 mm to 9.8 mm and a thickness of 0.05 mm to 0.5 mm. Such convex portions 3A can be formed, for example, by processing a metal using a mold corresponding to these shapes.

9 and 10, the case 3 is composed of two parts: a bottom plate 5 which is the lower wall, and a cap-shaped lid part having a top plate 4 which is the upper wall and a tubular part 6 which is the side wall, and the side (outer peripheral surface) of the bottom plate 5 and the lower end of the inner surface of the lid part (tubular part 6) are joined by, for example, welding. The case 3 may have the outer edge of the upper surface of the bottom plate 5 and the lower end of the lid part joined. The configuration of the case 3 is not limited to this. Contrary to the example shown in FIG. 9 and FIG. 10, the case 3 may be composed of two parts: a plate-shaped lid part which is the upper wall, and a cup-shaped container having a tubular part 6 which is the side wall and a bottom plate 5 which is the lower wall. Alternatively, the case 3 may be composed of two parts: a cap-shaped lid part which has a top plate 4 which is the upper wall and a tubular part which is the upper side wall, and a cup-shaped container having a tubular part which is the lower side wall and a bottom plate 5 which is the lower wall. Furthermore, the case 3 may be composed of three parts: a top plate 4 which is the upper wall, a cylindrical portion 6 which is the side wall, and a bottom plate 5 which is the lower wall.

9 and 10, two through holes 5A are formed in the bottom plate 5 of the case 3. A lead terminal 7 is inserted into each of the through holes 5A, and an insulating sealant 8 such as glass or resin is filled between the lead terminal 7 and the inner surface of the through hole 5A. The lead terminal 7 is fixed to the case 3 (bottom plate 5) by the sealant 8. The end of the lead terminal 7 in the internal space and the external electrode 40 of the piezoelectric element 1 are electrically connected via a lead wire 9 and a bonding material such as solder. This allows the voltage signal generated in the piezoelectric element 1 to be output to the outside via the lead terminal 7. The lead terminal 7 may be directly bonded to the external electrode 40 of the piezoelectric element 1 by a bonding material without the lead wire 9. If the external electrode 40 and the lead terminal 7 are connected via a lead wire 9 that is more flexible than the lead terminal 7, the stress applied to the connection between the external electrode 40 and the lead wire 9 due to the expansion and contraction of the piezoelectric element 1 can be reduced. Furthermore, a through hole may be provided in the top plate 4 of the case 3, and the lead terminal 7 may be provided so as to extend from the top surface of the case 3 to the outside. The length of the lead terminal 7 protruding from the outer surface of the case 3 may be set to, for example, 1 mm to 10 mm. The lead terminal 7 may be a wire made of a metal such as an enamel-coated copper wire, having a diameter of 0.1 mm to 1.0 mm and a length of 1.5 mm to 25 mm. The lead wire 9 is a wire made of a metal such as a copper wire, having a diameter of 0.1 mm to 1.0 mm and a length of 1.0 mm to 5.0 mm, and is joined to the lead terminal 7 by, for example, spot welding or the like.

Further advantages and other aspects can be readily derived by those skilled in the art. Therefore, the broader aspects of the disclosure are not limited to the specific details and representative embodiments shown and described above. Thus, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 1 Piezoelectric element 10 Laminate 11 Active region 12 Inactive region 20 Piezoelectric body 30 Internal electrode 35 Connection portion 36 First portion 37 Second portion 40 External electrode 43 Third portion 50, 60 Layer 100 Piezoelectric sensor

Claims (11)

a laminate in which a plurality of piezoelectric bodies and internal electrodes are laminated;
an external electrode located on a side surface of the laminate and connected to the internal electrode;
The laminate comprises:
an active region sandwiched between the internal electrodes having different polarities;
and an inactive region sandwiched between the internal electrodes having the same polarity;
The internal electrodes contain Ag and Pd as main components,
an active portion of the internal electrode located in the active region is a first portion;
an inactive portion of the internal electrode located in the inactive region has a second portion having a higher Pd content than the first portion;
The first portion has a higher Au content than the second portion. The piezoelectric element according to claim 1 , wherein the internal electrode located at the boundary between the active portion and the inactive portion has a higher Ag content than the inactive portion. The piezoelectric element according to claim 1 , wherein the external electrode is located within the second portion in a side view. The external electrodes contain Au as a main component,
a connection portion located between the inactive portion and the external electrode,
4. The piezoelectric element according to claim 1, wherein the connecting portion contains an alloy of Au and Pd. The piezoelectric element according to claim 4 , wherein the connection portion has a lower content of Ag and Pd than the active portion. 6. The piezoelectric element according to claim 1, further comprising a portion containing Ag, the portion being located between the inactive portion and the external electrode. The piezoelectric element of any one of claims 1 to 6, wherein the external electrode is positioned overlapping the internal electrode in a planar view, has a third portion containing Ag, and the width of the third portion along the thickness direction of the internal electrode is larger on the outer edge side than in a central portion along the width direction of the internal electrode. The laminate contains Pd,
8. The piezoelectric element according to claim 1, wherein the external electrodes contain Pb at interfaces with the laminate. The external electrodes contain Au and Ag as main components,
A first region contacting the laminate and a second region exposed to the outside,
The first region has a higher Ag content than the second region,
9. The piezoelectric element according to claim 1, wherein the second region has a higher content of Au than the first region. the external electrode has a first layer in contact with the laminate and a second layer exposed to the outside,
The first layer contains Ag as a main component,
9. The piezoelectric element according to claim 1, wherein the second layer contains Au as a main component. A piezoelectric sensor comprising a piezoelectric element according to any one of claims 1 to 10.

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